LysoPC(P-18:1(9Z)) is a lysophospholipid (LyP). It is a monoglycerophospholipid in which a phosphorylcholine moiety occupies a glycerol substitution site. Lysophosphatidylcholines can have different combinations of fatty acids of varying lengths and saturation attached at the C-1 (sn-1) position. Fatty acids containing 16, 18 and 20 carbons are the most common. LysoPC(P-18:1(9Z)), in particular, consists of one chain of plasmalogen 18:1n9 at the C-1 position. The plasmalogen 18:1n9 moiety is derived from animal fats, liver and kidney. Lysophosphatidylcholine is found in small amounts in most tissues. It is formed by hydrolysis of phosphatidylcholine by the enzyme phospholipase A2, as part of the de-acylation/re-acylation cycle that controls its overall molecular species composition. It can also be formed inadvertently during extraction of lipids from tissues if the phospholipase is activated by careless handling. In blood plasma significant amounts of lysophosphatidylcholine are formed by a specific enzyme system, lecithin:cholesterol acyltransferase (LCAT), which is secreted from the liver. The enzyme catalyzes the transfer of the fatty acids of position sn-2 of phosphatidylcholine to the free cholesterol in plasma, with formation of cholesterol esters and lysophosphatidylcholine. Lysophospholipids have a role in lipid signaling by acting on lysophospholipid receptors (LPL-R). LPL-R's are members of the G protein-coupled receptor family of integral membrane proteins. Plasmalogens are glycerol ether phospholipids. They are of two types, alkyl ether (-O-CH2-) and alkenyl ether (-O-CH=CH-). Dihydroxyacetone phosphate (DHAP) serves as the glycerol precursor for the synthesis of plasmalogens. Three major classes of plasmalogens have been identified: choline, ethanolamine and serine derivatives. Ethanolamine plasmalogen is prevalent in myelin. Choline plasmalogen is abundant in cardiac tissue. Usually, the highest proportion of the plasmalogen form is in the ethanolamine class with rather less in choline, and commonly little or none in other phospholipids such as phosphatidylinositol. In choline plasmalogens of most tissues, a higher proportion is often of the O-alkyl rather than the O-alkenyl form, but the reverse tends to be true in heart lipids. In animal tissues, the alkyl and alkenyl moieties in both non-polar and phospholipids tend to be rather simple in composition with 16:0, 18:0 and 18:1 (double bond in position 9) predominating. Ether analogues of triacylglycerols, i.e. 1-alkyldiacyl-sn-glycerols, are present at trace levels only if at all in most animal tissues, but they can be major components of some marine lipids.

This compound belongs to the class of organic compounds known as 1-(1z-alkenyl)-glycero-3-phosphocholines. These are glycerophosphocholines that carry exactly one 1Z-alkenyl chain attached at the O1 position of a glycerol moiety through an ether linkage.

Has transacylase and calcium-independent phospholipase A2 activity. Catalyzes the formation of 1-O-acyl-N-acetylsphingosine and the concomitant release of a lyso-phospholipid (By similarity). May have weak lysophospholipase activity.

PA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. This isozyme hydrolyzes more efficiently L-alpha-1-palmitoyl-2-oleoyl phosphatidylcholine than L-alpha-1-palmitoyl-2-arachidonyl phosphatidylcholine, L-alpha-1-palmitoyl-2-arachidonyl phosphatidylethanolamine, or L-alpha-1-stearoyl-2-arachidonyl phosphatidylinositol. May be involved in the production of lung surfactant, the remodeling or regulation of cardiac muscle.

Selectively hydrolyzes arachidonyl phospholipids in the sn-2 position releasing arachidonic acid. Together with its lysophospholipid activity, it is implicated in the initiation of the inflammatory response.

PA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. Has a powerful potency for releasing arachidonic acid from cell membrane phospholipids. Prefers phosphatidylethanolamine and phosphatidylcholine liposomes to those of phosphatidylserine.

Catalyzes the release of fatty acids from phospholipids. It has been implicated in normal phospholipid remodeling, nitric oxide-induced or vasopressin-induced arachidonic acid release and in leukotriene and prostaglandin production. May participate in fas mediated apoptosis and in regulating transmembrane ion flux in glucose-stimulated B-cells. Has a role in cardiolipin (CL) deacylation. Required for both speed and directionality of monocyte MCP1/CCL2-induced chemotaxis through regulation of F-actin polymerization at the pseudopods.
Isoform ankyrin-iPLA2-1 and isoform ankyrin-iPLA2-2, which lack the catalytic domain, are probably involved in the negative regulation of iPLA2 activity.

Central enzyme in the extracellular metabolism of plasma lipoproteins. Synthesized mainly in the liver and secreted into plasma where it converts cholesterol and phosphatidylcholines (lecithins) to cholesteryl esters and lysophosphatidylcholines on the surface of high and low density lipoproteins (HDLs and LDLs). The cholesterol ester is then transported back to the liver. Has a preference for plasma 16:0-18:2 or 18:O-18:2 phosphatidylcholines. Also produced in the brain by primary astrocytes, and esterifies free cholesterol on nascent APOE-containing lipoproteins secreted from glia and influences cerebral spinal fluid (CSF) APOE- and APOA1 levels. Together with APOE and the cholesterol transporter ABCA1, plays a key role in the maturation of glial-derived, nascent lipoproteins. Required for remodeling high-density lipoprotein particles into their spherical forms.

PA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. L-alpha-1-palmitoyl-2-linoleoyl phosphatidylethanolamine is more efficiently hydrolyzed than the other phospholipids examined.

Modulates the action of platelet-activating factor (PAF) by hydrolyzing the sn-2 ester bond to yield the biologically inactive lyso-PAF. Has a specificity for substrates with a short residue at the sn-2 position. It is inactive against long-chain phospholipids.

Acyltransferase which mediates the conversion of lysophosphatidylcholine (1-acyl-sn-glycero-3-phosphocholine or LPC) into phosphatidylcholine (1,2-diacyl-sn-glycero-3-phosphocholine or PC) (LPCAT activity). Catalyzes also the conversion of lysophosphatidylserine (1-acyl-2-hydroxy-sn-glycero-3-phospho-L-serine or LPS) into phosphatidylserine (1,2-diacyl-sn-glycero-3-phospho-L-serine or PS) (LPSAT activity). Has also weak lysophosphatidylethanolamine acyltransferase activity (LPEAT activity). Favors polyunsaturated fatty acyl-CoAs as acyl donors compared to saturated fatty acyl-CoAs. Seems to be the major enzyme contributing to LPCAT activity in the liver. Lysophospholipid acyltransferases (LPLATs) catalyze the reacylation step of the phospholipid remodeling pathway also known as the Lands cycle.

Possesses both acyltransferase and acetyltransferase activities. Activity is calcium-independent. Mediates the conversion of 1-acyl-sn-glycero-3-phosphocholine (LPC) into phosphatidylcholine (PC). Displays a clear preference for saturated fatty acyl-CoAs, and 1-myristoyl or 1-palmitoyl LPC as acyl donors and acceptors, respectively. May synthesize phosphatidylcholine in pulmonary surfactant, thereby playing a pivotal role in respiratory physiology.

Possesses both acyltransferase and acetyltransferase activities. Activity is calcium-dependent. Involved in platelet-activating factor (PAF) biosynthesis by catalyzing the conversion of the PAF precursor, 1-O-alkyl-sn-glycero-3-phosphocholine (lyso-PAF) into 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF). Also converts lyso-PAF to 1-alkyl-phosphatidylcholine (PC), a major component of cell membranes and a PAF precursor. Under resting conditions, acyltransferase activity is preferred. Upon acute inflammatory stimulus, acetyltransferase activity is enhanced and PAF synthesis increases (By similarity).

Calcium-dependent phospholipase A2 that selectively hydrolyzes glycerophospholipids in the sn-2 position with a preference for arachidonoyl phospholipids. Has a much weaker activity than PLA2G4A. Isoform 3 has calcium-dependent activity against palmitoyl-arachidonyl-phosphatidylethanolamine and low level lysophospholipase activity but no activity against phosphatidylcholine. Isoform 5 does have activity against phosphatidylcholine.